iSimangaliso celebrates first World Mangrove Day

1 Aug 2016

The universal importance of iSimangaliso as a protected area is once again highlighted by the United Nations Educational, Scientific and Cultural Organization’s (UNESCO) declaration of July 26 2016, as the first “International Day for the Conservation of the Mangrove Ecosystem”. The World Heritage Site provides ideal habitat for mangrove ecosystems in South Africa, from its Kosi Bay/Mozambique border to the southernmost region of the Lake St Lucia Estuary, with six species recorded.

Says iSimangaliso CEO Andrew Zaloumis, “There are a thousand reasons reinforcing the wisdom of conserving iSimangaliso as a World Heritage Site, and UNESCO has just identified one more of these. With half of the world’s mangroves already lost, iSimangaliso has more mangrove types than anywhere else in the country and has the southernmost distribution of three of these. Mangroves are iconic and intimately associated with a diversity of fauna as well as cultural traditions that add to the uniqueness of this place of miracles.”

Dr Scotty Kyle, Ezemvelo KZN Wildlife senior ecologist based at Kosi Bay, confirms that five species of mangrove naturally occur within iSimangaliso: Avicennia marina (White mangrove); Bruguiera gymnorrhiza (Black mangrove); Rhizophora mucronata (Red mangrove); Ceriops tagal (Eastern mangrove) and Lumnitzera racemosa (Kosi mangrove). A single specimen of a sixth mangrove species, the Xylocarpus granatum (Cannonball mangrove) has been found at Kosi Bay. The latter three reach their southern limit of distribution at Kosi Bay, while the white, black and red mangroves also occur in the southern estuaries of iSimangaliso.

Mangroves are usually found in tropical climates, within the littoral zone and specifically in sheltered shores. The mangrove environment is a finely-balanced living community. UNESCO reports that over half of the world’s mangrove forests have been lost in the last century, many of them to aquaculture, agriculture, and development. The dozens of diverse mangrove species, which live in tropical and subtropical tidal flats around the world, have in common a tolerance for salt water. Mangrove trees are halophytes – salt-resistant plants with special adaptive mechanisms for coping with conditions of high salinity. The mangrove swamp is a dynamic community, continuously adapting to varying conditions. The forests provide important habitat for a diverse array of marine species and protect coasts from storms.

Animals and Mangroves

Many animals are considered permanent residents of the mangrove ecosystem while others are seen as opportunistic visitors, or dependent on estuaries to complete their life cycles. These include invertebrates, zooplankton, crustaceans, molluscs, amphibians, fish, reptiles, birds and mammals – all connected in some way to this remarkable ecosystem. Within iSimangaliso, animals commonly associated with the habitat include hippo (with over 800 hippo occurring in the Park) and Nile crocodiles (upwards of 1200 adults). Fish eagles, kingfishers, herons, cormorants, storks and numerous other birds are commonly seen amongst the Park’s mangroves. One of the most characteristic residents of a mangrove swamp is the fiddler crab, noticeable by one huge vibrantly coloured claw. Of the 94 known species worldwide, five occur in South African estuaries where the mudflats are pockmarked by their burrows.

(Left) According to estuarine ecologist Nicolette Forbes, the climbing whelk (Cerithidea decollata) pictured here climbs up the trunks of mangroves during the tidal cycle with snail numbers building up on the trees during spring tides and decreasing over neap tides. “The indication is that tree ascent is based on predator avoidance,” says Nicolette, adding that whelks are quite fascinating in having a built-in activity rhythm that enables them to ascend trees well before tidal flooding reaches them (Photo credit Nicolette Forbes). (Right) Hippos wallowing amongst mangroves is a typical daily scene in iSimangaliso’s Lake St Lucia Estuary.(Left) A Giant kingfisher contemplates its next meal in Lake St Lucia’s mangrove swamps; (Right) Fish eagles are common sightings in the Park.The Avicennia marina is a common sight along the Lake St Lucia Estuary shores. The trees can attain a height of up to 12 metres and have a smooth, whitish grey bark. Visitors on the estuary boat cruises will notice these trees surrounded by ‘pencil roots’ (unbranched aerial pneumatophores) which enable the plant to ‘breathe through its toes’.

Natural resource use

At the Kosi Bay section of the Park, the mangroves form part of a centuries-old system of fish traps, representing the sustainable use of a natural resource. The wood from several mangrove species is used for poles to create the traps along with other uses in the local community such as building materials, fishing poles, tanning and firewood. The local names of these mangroves include isikhangazi, isihlobane, isinkaha, umhlume, isikaha-esimhlophe and isibhaha-esibomvu, indicating that they have long been known in traditional culture.The extremely hard wood – a factor of its high tannin content to combat salt – is resistant to rotting in the tidal waters and the closely woven structures create an ideal environment for other creatures such as eels and barnacles. Traps date back over 700 years and are passed down through the family line.